The invention relates to a control of the ultra-filtration in connection with hemodialysis. A control apparatus controls the alternate supply or withdrawal of fresh and used dialysis solution into one or the other or out of one or the other chamber of at least one balancing apparatus and for controlling the drive of an ultra-filtration pump for an additional withdrawal of used dialysis solution out of the dialyzer circulatory system.
A known method for the discontinuous measuring of the liquid withdrawal per unit of time resides in that the dialyzer solution flow to the dialyzer is temporarily interrupted by means of switch-over valves and in that the outflow conduit of the dialyzer is connected with a through flow meter for reading the liquid withdrawal per unit of time. By means of additional steps the pressure difference beween the blood side and the dialyzing solution side is kept constant on the previous operational value. Thus, the passage of liquid through the membrane during the measuring is about the same as during the normal operation. It is disadvantageous, that each time it is necessary to interrupt the operation so that a continuous measuring is not possible according to said method. Further, with said method only one measuring possibility is provided. In order to achieve a determined value of the liquid quantity to be withdrawn it is necessary to evaluate the measured results and to make a corresponding manual correction of the operating values in the apparatus at relatively short time intervals.
It is known from U.S. Pat. No. 4,113,614 to automate the control of the pressure across the membrane in a hemodialysis apparatus and also to automate the control of the ultra-filtratior rate by metering and monitoring the ultra-filtration rate and the total quantity of ultra-filtrate removed. One embodiment of this U.S. Pat. No. 4,113,614 which was issued on Sept. 12, 1978, requires a dialysis solution reservoir having a constant volume. In another embodiment of this prior art two pumps are used having exactly corresponding pumping rates for the supply and discharge of dialysis solution, whereby a dynamically closed system is provided. However, it is in practice very difficult to construct pumps in an economically feasible way, which have exactly corresponding pumping rates.
U.S. Pat. No. 4,113,614 also discloses a special pump for the withdrawal of liquid from the dynamically closed system in such a quantity that the quantity of withdrawn liquid corresponds to the ultra-filtration quantity. A piston pump is disclosed for this purpose which is also utilized simultaneously for r:easuring the pumped quantity and, based on the assumed proportionality of the driving force for the pump and the working pressure of the pump, for measuring the pressure. This type of apparatus leaves room for improvement, especially with regard to the problem of proportioning the concentrate and water. More specifically, the preparation of the dialysis solution from concentrate and water in exactly predetermined ratios in combination with the supply and removal of liquid quantities corresponding to each other may be improved upon, particularly if these mentioned partial functions are to be directly combined or linked with each other as is the purpose of the present invention.
An article by Harold P. McDonald, Jr., entitled "Automatic Peritoneal Dialysis Machine for Hospital or Home Peritoneal Dialysis; Preliminary Report" appeared in volume 15 of the "Transactions of the American Society of Artificial Internal Organs", (1969) starting at page 108 and ending on page 111. A peritoneal dialysis apparatus is not necessarily suitable for hemodialysis purposes. For example, in a peritoneal dialysis apparatus a single state system is used in a discontinuous operation with piston pumps. The ultra-filtration is not controlled and the ultra-filtrate quantity may be measured only at certain times, namely, at the end of the flow out time by measuring the liquid level in the flow out container. Thus, the teachings applicable to a peritoneal dialysis apparatus are not suitable for a hemodialysis apparatus especially where the latter is supposed to operate continuously in a push-pull fashion to assure a continuous, uniform flow through the dialyzer. Moreover, the control of the ultra-filtration with a predetermined ultra-filtration rate in terms of ultra-filtration quantity per unit of time, as well as a continuous indication of the accumulated ultra-filtration quantity, is not taught by McDonald, Jr.
U.S. Pat. No. 4,037,616 (Pinkerton) discloses certain features which are also employed according to the present invention, for example, the use of balancing chamber components operated in a push-pull type of system. However, Pinkerton actually uses the diaphragms and piston means or at least piston rods which extend through the chamber walls and thus cause leakage problems at the points where the piston rods extend through the chamber walls, see for example FIGS. 1, 3, and 4 of Pinkerton. The type of liquid used in dialysis comprises a high proportion of salt and glucose in solution. Therefore, there is a strong tendency for these components in solution to crystallize, and experience has shown that such crystallization takes place on the piston rods, whereby the sealings at the passage points through the chamber walls are damaged by the crystalline material. This crystallization is a continuous process and once a leakage has formed it grows rapidly.
Moreover, in this environment it is, for the patient's health, very important to keep the entire system free of infection causing agents. Piston rods as in Pinkerton cannot be kept entirely free of such infecting agents because the piston rods extend into and out of the balancing chamber components.
Kunitomo et al in the article "Controlled Ultrafiltration With Hemodialysis", Trans. Am. Soc. Int. Organs, Volume 23, pages 234 to 242 (1977) also do not disclose the combination of teachings for the proportional mixing of the two components which are used to make fresh dialysis solution and there is also no teaching in Kunitomo et al to combine the mixing with a balancing operation. While it is true that Kunitomo et al disclose a degasser in FIG. 2 on page 235, applicant does not claim a degasser per se.
A second Pinkerton U.S. Pat. No. 4,054,522 also suffers the same defects as the first mentioned Pinkerton reference (U.S. Pat. No. 4,037,616) and the comments above apply also to the second Pinkerton reference including FIG. 3 thereof.
U.S. Pat. No. 3,976,574 (White) shows two degassers (22) and (26). However, these two degassers or aerators are connected in series through the mixer (24) and hence both aerators are effective on the liquid which is supplied to the dialyzer (10). According to the present invention the aerators or degassing means are arranged quite differently. The present invention is more importantly concerned with balancing and ultra-filtration control.
U.S. Pat. No. 3,795,318 (Crane et al) was primarily cited for its pressure sensing features. However, the present invention is not exhausted by such a feature and aims at a switch-over of the balancing chamber components from push to pull and vice versa in response to a pressure sensing. Thus, the respective valve means at the inlets of the balancihg chamber components are switched from one into the other position if the pressure in the return conduit from the dialyzer at the outlet of the pump (67) in FIG. 8 exceeds a predetermined pressure value.
The control of a switch in response to a pressure sensitive element is shown in U.S. Pat. No. 3,709,222 (DeVries) "Method And Apparatus For Automatic Peritoneal Dialysis", however, the just mentioned reference does not disclose the combination of the features set forth hereafter. Therefore, even if the disclosure of DeVries is combined with the disclosure of the Pinkerton reference U.S. Pat. No. 4,037,616 the teachings of the present inventicn cannot be found.
U.S. Pat. No. 4,060,485 (Eaton) shows the use of a "computer" in a dialysis apparatus. However, there are no details shown in the Eaton reference to the effect that two temperature controlled heating units are employed for improving, or rather increasing the balancing precision as disclosed with reference to present FIG. 4. The present temperature controlled system of the present application assures that the temperature difference between the inflowing and outflowing dialysate is substantially zero and that the temperature of the dialysate in the dialyzer corresponds to the patient's temperature. No such teaching is disclosed by Eaton.
U.S. Pat. No. 4,113,614 shows an ultra-filtration rate read-out unit. However, the present invention is not exhausted by such a feature.
U.S. Pat. No. 3,352,779 discloses the filling of the hemodialyzer prior to its operation. While it is necessary to fill the dialyzer prior to its operation, Austin et al do not give any hint of the specific way this is accomplished according to the present invention.
U.S. Pat. No. 4,054,522 shows, in FIG. 3, the sequential arrangement of a dosing and mixing system (A) with a degassing system (B) and the ultra-filtration system (C). These three systems (A, B, and C) of U.S. Pat. No. 4,054,522 operate substantially independently of one another. Therefore, the cooperation as set forth in the present case of the proportioning and mixing system with the remaining features is not disclosed in U.S. Pat. No. 4,054,522. According to the present invention the concentrate only is directly dosed and the water is dosed indirectly. The balancing system acts as a meter for the quantity of used-up dialysis solution whereby a connection between the balancing function and the proportioning is accomplished. This is not shown in U.S. Pat. No. 4,054,522.
French patent No. 2,344,297 shows the use of an alarm in a hemodialysis system when the blood transfer level is not acceptable. Although this French patent shows two balancing chambers, it does not disclose the functional or operational combination of the balancing operation with the dosing and mixing operation. Further, the detector in French reference No. 2,344,297 is a hemoglobin detector in the form of a "colorimeter 23" which cannot be compared with the present blood leakage detector (65) in FIG. 8.
German patent Publication No. 2,544,258 which is based on another invention of the present inventor, was also cited for the alarm feature. In this earlier system, of the present inventor, the operation is not a push-pull operation so that a filling step is required between two working steps or strokes. During the filling step dialysate does not flow through the dialyzer. Mcreover, the balancing is not directly related to the dialysis solution as it is prepared and flowing into the dialyzer. In this reference the components of water and concentrate on the one hand, and the used-up dialysis solution on the other hand, are balanced.
In French patent No. 2,345,165 the production of the dialysis solution with the step of proportional mixing of the concentrate and water is independent of the balancing and independent of the ultra-filtration control. Therefore, a more detailed discussion of this reference does not appear to be necessary.
Netherlands' patent Publication 7,701,451 appears to be quite similar to the Pinkerton reference U.S. Pat. No. 4,037,616 which has been discussed in detail above. Therefore, a further discussion of the Dutch reference would appear to be unnecessary.
Ivanovich et al in the article "A Compact Hydraulic Proportioning System For Hemodialysis", Trans. Am. Soc. Int. Organs, Vol. 12, pages 357 to 361 (1966) provides an alternative to the French patent No. 2,344,297 with regard to the alarm feature and is pertinent only to that feature. Therefore, a further discussion of this Ivanovich et al reference does not appear to be necessary. Furthermore, in Ivanovich et al the water and concentrate are dosed by piston pumps. Contrary thereto according to the present invention, the through flow of the ready dialysis solution already mixed is measured and this measuring controls the portion-wise supply of the concentrate to a mixing point arranged upstream of the balancing chamber.
Applicant notes the following additional references, all of which may be clearly distinguished from the present invention: